1. Field of the Invention
The present invention relates to portable intruder alarm systems used to detect the opening of a door. More particularly, the device of the present invention pertains to those portable intruder alarm systems which are hung from the top of a door and engage the wall above the door as the door is closed.
2. Description of the Prior Art
Some of the portable door intruder alarms which are attached to the top of a door sound an alarm once the door is opened by detecting the motion of a biased member pushing against the wall above the door as the door is closed with the device attached thereto. Various arrangements are provided in the prior art for attaching the device to the door and for detecting the opening of the door.
U.S. Pat. No. 3,261,010 issued Jul. 12, 1966 to John V. Kardel illustrates a portable door alarm having a fixed plate extending up from the back thereof with a slit therethrough for allowing a clamp to slide therein across the top of the device. The clamp includes a downward protruding leg member at the back thereof to secure the device to a door. A finger, which normally extends vertically from the top rear of the device engages the wall when the door is shut with the device attached thereto so as to push the finger forward as it makes contact with the wall above the door. Once set, the alarm device will sound a horn if the finger returns to its normal position towards the rear of the device.
U.S. Pat. No. 3,878,539 issued Apr. 15, 1975 to Chadyeane Gooding discloses a portable door alarm having an L-shaped member with a slit through the elongated portion thereof. A screw attaches to the top of the device through the slit allowing the L-shaped member to serve as an adjustable bracket, securing the device to the top of a door. A coil arm having a tip member extends from the top of the device and is normally located near the rear wall thereof so that the tip member engages the wall above the door and pushes the coil arm forward when the door is closed with the device attached thereto. If the alarm is set, and the door is opened the coil arm returns to its normal rearward location and sounds a warning device.
U.S. Pat. No. 4,059,832 issued Nov. 22, 1977 to LeRoy T. Conklin discloses an portable door alarm having an L-shaped member having a bracket at the end of an elongated portion. The elongated portion is hingeably attaching to the bottom end of the back of the device. The hinge has a torsion spring biasing the hook towards the back of the device. When the bracket is placed over the top of a door, the spring biases top portion of the device towards the door. The top portion extends above the door when the hook portion is placed over the top of the door. A pushbutton extends out from the back of the top portion and engages the wall above the door when the door is closed with the device attached thereto. With the device set and the door closed, the pushbutton is pressed down due to the force of the torsion spring holding the top portion of the device against the wall. If the door is then opened so that the pushbutton extends to its normal position, a buzzer alarm sounds.
U.S. Pat. No. 4,484,181 issued Nov. 20, 1984 to Frederic W. Schwartz discloses a portable burglar alarm having an L-shaped elongated member slidably extending along the length of the device and being spring biased to pull the smaller leg portion thereof towards one side thereof. The leg is able to engage the outside of the door and pull the one side towards the front side of the door, thus maintaining the device on the top of the door. A lever at the top of the is biased towards the wall above the door through the use of a torsion spring so as to engage the wall. If the door is opened with the device attached thereto and the alarm set, the lever is rotated towards the wall and a horn is activated.
U.S. Pat. No. 4,808,974 issued Feb. 28, 1989 to Richard E. Cantley discloses a portable door alarm adapted to be removably mounted on the top edge of an inwardly swinging door. The device has an adjustable mounting bracket which extends from one end of the top of the device to the other and has a downwardly protruding leg to engage the outside portion of the door along the top thereof. The bracket includes several slots at the ends thereof a pair of screws, one at each end, are inserted to secure the bracket in a fixed adjustable position. A middle slot through the bracket allows a lever to project therethrough above the top of the device. The lever is biased to move behind the back of the device so as to engage a wall above the device once attached to the top of a door with the door shut. The lever is pushed forward when contacting the wall as the door is closed. When the door is opened with the alarm set on the device, a buzzer sounds when the lever moves backwards as the door is opened and the top of the wall no longer engages the lever.
U.S. Pat. No. 5,072,212 issued Dec. 10, 1991 to Gary R. Sorenson discloses a portable alarm device having a pair of brackets extending out from the rear of the device. As the door is closed, a trip switch lever extending from the top of the device is biased to engage a wall above the device once the door is closed. The device is activated and a buzzer sounds, once the door is opened and the lever disengages the wall.
None of the above patents, taken either singly or in combination, is seen to describe the instant invention as claimed.